1. Field of the Invention
The invention relates to a high frequency transistor having a small emitter width and a low base bulk resistance, which, in a semiconductor body is electrically insulated from adjacent components by oxide layers.
2. Description of the Prior Art
In order to achieve as high as possible a degree of integration in integrated circuits, frequently high frequency transistors having a small emitter width and a small base bulk resistance are required. Usually, the minimum emitter width is determined by the lower limit values which can be attained with photo-lacquer- and etching-techniques. Furthermore, the base bulk resistance can be reduced by implanting a stepped profile (IEEE Transactions on Electron Devices, Vol. ED 21 No. 4, April 1974, pages 273-278).
As is known, the oxide insulation technique has the advantage that no insulating tubs with lateral insulation diffusions are required in order to electrically isolate a component from an adjacent component. Thus a higher degree of integration can be achieved with the oxide insulation technique.